\begin{tikzpicture}
    \draw (-.9,0) circle [x radius = 2cm, y radius = .8cm];
    \draw ( .9,0) circle [x radius = 2cm, y radius = .8cm];
    \draw (   0,0) node {正方形集合};
    \draw (-2.0,0) node {矩形集合};
    \draw ( 2.0,0) node {菱形集合};
\end{tikzpicture}

